This invention relates to a new piezoelectric ceramic material.
Piezoelectric transformers made of piezoelectric ceramic materials have attracted great attention from the public, due to their excellent high voltage performance, such as high voltage step-up ratio, small dimensions, light weight, and high break-down voltage, as well as their being not destructible by short circuit, using no metallic material, being damp-proof, causing no electro-magnetic disturbance, etc.. Endeavours have been made to continuously improve the properties of the existing piezoelectric ceramic materials of binary system (PZT), ternary (PCM, PSM), or their varieties. However, some properties, such as temperature characteristic, mechano-electric coupling coefficient, mechanical quality factor, mechanical strength, etc., can not yet satisfy the requirement of large power output, and it is impossible to make with such materials a piezoelectric transformer having a single-piece output power higher than 40 W. To give a few examples, the highest output power of a piezoelectric transformer produced by the Sumitomo Electric Company of Japan is 40 W (see Kawata Yoshikawo, "Electric Expectation" Vol. 7(1970), No. 5, P. 67); the highest output power of a piezielectric transformer using improved PCM material produced by the Shandong University of China is 19 W (see Zhu Feng-Zhu, "Physics", Vol. 2 (1973), No. 4, pp. 183-190); and the highest output power of a piezielectric transformer using PSM material produced by the Qinhua University of China is 5.6 W (see "Ferroelectrics", Vol. 28, (1980), pp. 402-406).